I am currently raising 23 chicks (5 Silver Laced. 5 Buff Orpingtons, 4 Partridge Rocks, and 9 Barred Rocks) along with 2 Cayuga Ducks. All are about 2 1/2 weeks old. I have read that at 3 weeks I should start lower protein food for the Ducks. Question is, the chick starter I am using is 18% protein, can I continue to use that straight or can I also mix something with it?